A process for the protection of cultivated plants against harmful effects of aggressive agricultural chemicals by the use of compounds of the formula I ##STR1## wherein R.sub.1, R.sub.2 and R.sub.3 independently of one another are each hydrogen, halogen, C.sub.1 -C.sub.3 -alkyl, C.sub.1 -C.sub.3 -alkoxy, nitro or cyano,R.sub.4, R.sub.5 and R.sub.6 independently of one another are each hydrogen, halogen or C.sub.1 -C.sub.3 -alkyl,A is any one of the groups --CH.sub.2 --, --CH.sub.2 --CH.sub.2 -- or --CH(CH.sub.3)--, andZ is cyano, or amidoxime which can be acylated on the oxygen atom,including acid addition salts and metal complexes thereof.